Most of the time, the only way to tell what is propelling your BMW Active Hybrid 5 in heavy traffic is to glance at the rev-counter. If you're doing less than 60km/h and not actually accelerating, chances are it's the 40kW electric motor, and the rev-counter needle is stationary on zero - which is just as disconcerting as it sounds.

As soon as you accelerate even slightly, however, the needle jumps up to about 1500rpm (you don't feel or hear anything at all) and the stately Hybrid 5 proceeds on its way in plutocratic near-silence, gathering momentum while all around you lesser vehicles rev and spit and change gears and rev again, sounding just so 20th century.

Elitist? Yes. Revolutionary? Not really.

As with most hybrids, the first BMW petrol-electric to be released in South Africa demonstrates its green credentials best in an urban environment, which is why the first section of the launch drive took us through an industrial area north of Cape Town on a Friday mid-morning.

ANY TIME IT THINKS IT CAN GET AWAY WITH IT

And the cleverest part of the whole deal is that BMW has used the flexibility of the electric drive to take the idle-stop concept to the next level.

Whereas most idle-stop systems will only switch the engine off when the car is standing still, in neutral, with the brakes on, the Active Hybrid 5 will shut down the three-litre straight-six any time it thinks it can get away with it. And if you keep one eye on the rev-counter, it's astonishing just how often that is.

Even coasting downhill at close to the national speed limit, the engine will sometimes switch off, while the power diagram on the dashboard's central touchscreen shows the electric motor generating “engine braking” by converting momentum into amps, boosting both the car's batteries with energy that would normally be wasted as heat.

But when you touch the accelerator pedal, or even when the car comes to the bottom of the hill, the engine is there as needed, providing the superbly polished performance we have come to expect from BMW's big sixes.

POISE, PANACHE AND POWER

It's the same around the twisties; the extra weight of the electric motor and the lithium-ion battery pack (75kg in all) doesn't seem to affect the Hybrid 5's road manners at all; it disposes of corners with all the poise, all the panache and all the power of its conventional siblings.

A flick or two of the paddle shift going in, to get the revs up, and a bootful of loud pedal coming out will reward you with superbly modulated power and steering, a minimum of body roll and utter disdain for bumps and ridges in awkward places, all accompanied by that familiar six-cylinder BMW snarl, suitably restrained in this iteration as befits an executive carriage.